This proposal is designed to test the hypothesis that an increased intake of potassium coupled with a reduction in sodium intake, and/or calcium supplementation will prevent the expected age related increase in blood pressure and thereby forestall the development of hypertension. Of the many non-pharmacological interventions that have been proposed as strategies for hypertension prevention the majority of existing evidence favors our nutritional approach as the one most likely to yield significant results. As part of a collaborative approach to the study of non-pharmacologic interventions, we propose to enroll approximately 200 subjects, aged 25-49 in a randomized parallel trial which will test the previously stated hypothesis. The study will have a factorial design that results in the four groups assigned to the following treatment regimens: (1) Low sodium (less than 70 mEQ/day), high potassium (greater than 100 mEq/day) intake (2) Calcium supplementation with 1500 mg elemental calcium/day (3) Combination of the approaches in (1) and (2) (4) Placebo supplementation but no dietary modification The strategy to be used for dietary modification will be based, primarily, upon withdrawal of bread and cereals with isocaloric substitution of potatoes, rice and/or other vegetable sources of complex carbohydrates. Preliminary studies show that this will readily achieve our goal sodium (less than 70 mEQ/day) and potassium (greater than 100 mEq/day) intake levels with a molar sodium/potassium ration less than 1. A positive result that interrupts the expected increase in age related blood pressure would provide the basis for a most important hypertension prevention mass treatment strategy.